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09 September 2002 AGE-NC Project No. 98-0450 Page 3 of 6 sample ports_ These samples were labeled,placed in a pre-chilled cooler and transported of-custody to McCampbell Analytical. Laboratory Inc. (MAI) of Pacheco, California. The samples were analyzed for: • Total petroleum hydrocarbons as gasoline (TPH-g) in accordance with EPA Method 8015 Modified and • Benzene, toluene, ethylbenzene and xylene in accordance with EPA Method 8020. 2.4. SPARGE SYSTEM MONITORING The effect of the IAS system was monitored utilizing a YSI-55 dissolved oxygen meter eter on ground water. During-each monitoring event,the depth to ground water and percentage of dissolved oxygen ' were measured for available monitoring wells. General system maintenance and adjustments were performed at this time. The sparging flow rate was adjusted to approximately 4 standard cubic feet per minute (scfm) and to a pressure of 6 pounds per square inch (psi) at each well. 3.0. FINDINGS ' Ground water elevation, flow direction and gradient were determined from field data collected on 03 June 2002; the contaminant impact to ground water was quantified from the ground water laboratory data. From field data collected at the SVE remediation system between late March and early June 2002, AGE determined the average TPH-g concentration, the average flow rate and ' calculated the approximate mass and volume of gasoline removed. ' 3.1 RELATIVE GROUND WATER ELEVATION AND GRADIENT The depths to ground water from the tops of the monitoring well casings were measured at 47.70 to I 48.82 feet below surface grade (bsg). The corresponding ground water elevations ranged from 1.84 feet below mean sea level (MSL) in well BMW-5 to 3.06 feet below MSL in MW-5; however, based comparison of historical well elevations (Table 1), the ground water depth in well BMW-5 is ' assumed to be under-measured by exactly one foot. The value-presumed for well BMW-5 is 2:84 feet- below MSL. ISince the previous quarterly monitoring event, ground water elevation had increased an average 1 foot at the site. The ground water elevation data for the well network during the latest ground water monitoring event is depicted in Figure 3. The ground water flow direction was inferred to be ' southwards ata hydraulic gradient of approximately 0.0036ft/ft. Based on a southerly flow direction within the area contained by the six monitoring wells, wells MW-5 and BMW-2 would be down- ' Advanced GeoEnvironmcntaI,Inc.